Exit Zen
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string ID 13
type: paragraph
English
User-defined types are possible for the message body, where the type meets the __Body__ requirements. This simplified class declaration shows the customization points available to user-defined body types: ``` /// Defines a Body type struct body {
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string ID 33
type: paragraph
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} ```
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string ID 36
type: paragraph
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The meaning of the nested types is as follows
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string ID 38
type: table title
English
Body Type Members
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string ID 38
type: table cell
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Name
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string ID 38
type: table cell
English
Description
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string ID 38
type: table cell
English
`value_type`
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string ID 38
type: table cell
English
Determines the type of the [link beast.ref.boost__beast__http__message.body `message::body`] member.
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string ID 38
type: table cell
English
`reader`
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string ID 38
type: table cell
English
An optional nested type meeting the requirements of __BodyReader__, which provides the algorithm for storing a forward range of buffer sequences in the body representation. If present, this body type may be used with a __parser__.
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string ID 38
type: table cell
English
`writer`
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string ID 38
type: table cell
English
An optional nested type meeting the requirements of __BodyWriter__, which provides the algorithm for converting the body representation to a forward range of buffer sequences. If present this body type may be used with a __serializer__.
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string ID 66
type: heading
English
Value Type
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string ID 68
type: paragraph
English
The `value_type` nested type allows the body to define the declaration of the body type as it appears in the message. This can be any type. For example, a body's value type may specify `std::vector<char>` or `std::list<std::string>`. A custom body may even set the value type to something that is not a container for body octets, such as a [@boost:/libs/filesystem/doc/reference.html#class-path `boost::filesystem::path`]. Or, a more structured container may be chosen. This declares a body's value type as a JSON tree structure produced from a [@boost:/doc/html/json/input_output.html#json.input_output.parsing.streaming_parser `boost::json::stream_parser`]: ``` #include <boost/json/stream_parser.hpp>
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string ID 80
type: paragraph
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struct Body {
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string ID 86
type: paragraph
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}; ```
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string ID 89
type: paragraph
English
As long as a suitable reader or writer is available to provide the algorithm for transferring buffers in and out of the value type, those bodies may be parsed or serialized.
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string ID 95
type: section title
English
File Body __example__
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string ID 97
type: paragraph
English
Use of the flexible __Body__ concept customization point enables authors to preserve the self-contained nature of the __message__ object while allowing domain specific behaviors. Common operations for HTTP servers include sending responses which deliver file contents, and allowing for file uploads. In this example we build the [link beast.ref.boost__beast__http__basic_file_body `basic_file_body`] type which supports both reading and writing to a file on the file system. The interface is a class templated on the type of file used to access the file system, which must meet the requirements of __File__.
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string ID 108
type: paragraph
English
First we declare the type with its nested types:
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